1. Field of the Invention
The present invention relates to a printed circuit board and a method of manufacturing the same.
2. Description of the Background Art
Actuators are employed in drives such as hard disk drives. Such an actuator includes an arm arranged rotatably with respect to a rotation shaft and a suspension board used for a magnetic head that is attached to the arm. The suspension board is a printed circuit board for positioning the magnetic head with a desired track of a magnetic disk.
FIG. 11 is a vertical sectional view of a conventional suspension board (see JP 2004-133988 A, for example).
In the suspension board 910, a first insulating layer 904 is formed on a metal substrate 902. A write wiring trace W12 and a read wiring trace R12 are formed to be spaced apart from each other by a distance L1 on the first insulating layer 904.
A second insulating layer 905 is formed on the first insulating layer 904 to cover the write wiring trace W12 and the read wiring trace R12. On the second insulating layer 905, a write wiring trace W11 is formed at a position above the read wiring trace R12, and a read wiring trace R11 is formed at a position above the write wiring trace W12.
Each of the distance between the read wiring trace R11 and the write wiring trace W12 that are positioned one above the other and the distance between the read wiring trace R12 and the write wiring trace W11 that are positioned one above the other is L2.
In the suspension board 910 having the foregoing configuration, the distances between the write wiring traces W11, W12 and the read wiring trace R11 are substantially equal to the distances between the write wiring traces W11, W12 and the read wiring trace R12, respectively. Accordingly, it is considered that the magnitude of induced electromotive forces generated in the read wiring traces R11, R12 are substantially equal when write currents pass through the write wiring traces W11, W12. This allows a crosstalk between the write wiring traces W11, W12 and the read wiring traces R11, R12 to be reduced.
In recent years, it is desired to reduce characteristic impedance of the wiring traces in order to achieve lower power consumption of electronic equipment.